| The calorimeter at the left is at the Museum at the Department
of Natural Philosophy at Glasgow University in Scotland.
The label by the apparatus reads "Calorimeter by James Joule/1876/Used in his final determination". In the background are reproductions of illustrations from his 1876 determination of the mechanical equivalent of heat.
James Prescott Joule (1818-1889) had used a number of techniques to measure this quantity. His best known method used rotating paddles to stir water in a calorimeter. Thermometers of his own devising were used to measure the resulting temperature increase of the water, and falling weights provided the necessary mechanical energy. He first used this method in preliminary experiments in 1847 and in what he originally though were definitive measurements published in 1849. In the 1870s he returned to the technique, and used this calorimeter for his final determination of the mechanical equivalent of heat, in which he obtained a value of 4.1538 Joules/Kelvin. Of course, he did not use these units!
| The calorimeter at the left was made by Gaertner of Chicago
ca. 1930. Its double-walled metal outer container is filled with water,
and access holes allow the water to be stirred and its temperature measured.
The calorimeter can is inside the constant-temperature vessel.
The apparatus is in the Greenslade Collection.